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[dev.typeparams] runtime: simplify defer record allocation

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Now that deferred functions are always argumentless and defer
records are no longer with arguments, defer record can be fixed
size (just the _defer struct). This allows us to simplify the
allocation of defer records, specifically, remove the defer
classes and the pools of different sized defers.

Change-Id: Icc4b16afc23b38262ca9dd1f7369ad40874cf701
Reviewed-on: https://go-review.googlesource.com/c/go/+/326062
Trust: Cherry Mui <cherryyz@google.com>
Run-TryBot: Cherry Mui <cherryyz@google.com>
Reviewed-by: Michael Knyszek <mknyszek@google.com>
TryBot-Result: Go Bot <gobot@golang.org>
This commit is contained in:
Cherry Mui 2021-06-08 18:45:18 -04:00
parent 4468e1cfb9
commit e0e9fb8aff
6 changed files with 50 additions and 142 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

2
src/cmd/compile/internal/test/inl_test.go
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@ -42,7 +42,6 @@ func TestIntendedInlining(t *testing.T) {
"bucketMask",
"bucketShift",
"chanbuf",
"deferclass",
"evacuated",
"fastlog2",
"fastrand",
@ -63,7 +62,6 @@ func TestIntendedInlining(t *testing.T) {
"subtract1",
"subtractb",
"tophash",
"totaldefersize",
"(*bmap).keys",
"(*bmap).overflow",
"(*waitq).enqueue",

11
src/runtime/malloc.go
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@ -420,8 +420,6 @@ func mallocinit() {
throw("bad TinySizeClass")
}
testdefersizes()
if heapArenaBitmapBytes&(heapArenaBitmapBytes-1) != 0 {
// heapBits expects modular arithmetic on bitmap
// addresses to work.
@ -1088,15 +1086,6 @@ func mallocgc(size uintptr, typ *_type, needzero bool) unsafe.Pointer {
var scanSize uintptr
if !noscan {
// If allocating a defer+arg block, now that we've picked a malloc size
// large enough to hold everything, cut the "asked for" size down to
// just the defer header, so that the GC bitmap will record the arg block
// as containing nothing at all (as if it were unused space at the end of
// a malloc block caused by size rounding).
// The defer arg areas are scanned as part of scanstack.
if typ == deferType {
dataSize = unsafe.Sizeof(_defer{})
}
heapBitsSetType(uintptr(x), size, dataSize, typ)
if dataSize > typ.size {
// Array allocation. If there are any

8
src/runtime/mgc.go
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@ -1558,19 +1558,17 @@ func clearpools() {
sched.sudogcache = nil
unlock(&sched.sudoglock)
// Clear central defer pools.
// Clear central defer pool.
// Leave per-P pools alone, they have strictly bounded size.
lock(&sched.deferlock)
for i := range sched.deferpool {
// disconnect cached list before dropping it on the floor,
// so that a dangling ref to one entry does not pin all of them.
var d, dlink *_defer
for d = sched.deferpool[i]; d != nil; d = dlink {
for d = sched.deferpool; d != nil; d = dlink {
dlink = d.link
d.link = nil
}
sched.deferpool[i] = nil
}
sched.deferpool = nil
unlock(&sched.deferlock)
}

121
src/runtime/panic.go
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@ -236,7 +236,7 @@ func deferproc(fn func()) {
sp := getcallersp()
callerpc := getcallerpc()
d := newdefer(0)
d := newdefer()
if d._panic != nil {
throw("deferproc: d.panic != nil after newdefer")
}
@ -302,106 +302,37 @@ func deferprocStack(d *_defer) {
// been set and must not be clobbered.
}
// Small malloc size classes >= 16 are the multiples of 16: 16, 32, 48, 64, 80, 96, 112, 128, 144, ...
// Each P holds a pool for defers with small arg sizes.
// Assign defer allocations to pools by rounding to 16, to match malloc size classes.
const (
deferHeaderSize = unsafe.Sizeof(_defer{})
minDeferAlloc = (deferHeaderSize + 15) &^ 15
minDeferArgs = minDeferAlloc - deferHeaderSize
)
// defer size class for arg size sz
//go:nosplit
func deferclass(siz uintptr) uintptr {
if siz <= minDeferArgs {
return 0
}
return (siz - minDeferArgs + 15) / 16
}
// total size of memory block for defer with arg size sz
func totaldefersize(siz uintptr) uintptr {
if siz <= minDeferArgs {
return minDeferAlloc
}
return deferHeaderSize + siz
}
// Ensure that defer arg sizes that map to the same defer size class
// also map to the same malloc size class.
func testdefersizes() {
var m [len(p{}.deferpool)]int32
for i := range m {
m[i] = -1
}
for i := uintptr(0); ; i++ {
defersc := deferclass(i)
if defersc >= uintptr(len(m)) {
break
}
siz := roundupsize(totaldefersize(i))
if m[defersc] < 0 {
m[defersc] = int32(siz)
continue
}
if m[defersc] != int32(siz) {
print("bad defer size class: i=", i, " siz=", siz, " defersc=", defersc, "\n")
throw("bad defer size class")
}
}
}
var deferType *_type // type of _defer struct
func init() {
var x interface{}
x = (*_defer)(nil)
deferType = (*(**ptrtype)(unsafe.Pointer(&x))).elem
}
// Each P holds a pool for defers.
// Allocate a Defer, usually using per-P pool.
// Each defer must be released with freedefer. The defer is not
// added to any defer chain yet.
//
// This must not grow the stack because there may be a frame without
// stack map information when this is called.
//
//go:nosplit
func newdefer(siz int32) *_defer {
func newdefer() *_defer {
var d *_defer
sc := deferclass(uintptr(siz))
gp := getg()
if sc < uintptr(len(p{}.deferpool)) {
pp := gp.m.p.ptr()
if len(pp.deferpool[sc]) == 0 && sched.deferpool[sc] != nil {
if len(pp.deferpool) == 0 && sched.deferpool != nil {
// Take the slow path on the system stack so
// we don't grow newdefer's stack.
systemstack(func() {
lock(&sched.deferlock)
for len(pp.deferpool[sc]) < cap(pp.deferpool[sc])/2 && sched.deferpool[sc] != nil {
d := sched.deferpool[sc]
sched.deferpool[sc] = d.link
for len(pp.deferpool) < cap(pp.deferpool)/2 && sched.deferpool != nil {
d := sched.deferpool
sched.deferpool = d.link
d.link = nil
pp.deferpool[sc] = append(pp.deferpool[sc], d)
pp.deferpool = append(pp.deferpool, d)
}
unlock(&sched.deferlock)
})
}
if n := len(pp.deferpool[sc]); n > 0 {
d = pp.deferpool[sc][n-1]
pp.deferpool[sc][n-1] = nil
pp.deferpool[sc] = pp.deferpool[sc][:n-1]
}
if n := len(pp.deferpool); n > 0 {
d = pp.deferpool[n-1]
pp.deferpool[n-1] = nil
pp.deferpool = pp.deferpool[:n-1]
}
if d == nil {
// Allocate new defer+args.
systemstack(func() {
total := roundupsize(totaldefersize(uintptr(siz)))
d = (*_defer)(mallocgc(total, deferType, true))
})
// Allocate new defer.
d = new(_defer)
}
d.heap = true
return d
@ -424,23 +355,19 @@ func freedefer(d *_defer) {
if !d.heap {
return
}
sc := deferclass(0)
if sc >= uintptr(len(p{}.deferpool)) {
return
}
pp := getg().m.p.ptr()
if len(pp.deferpool[sc]) == cap(pp.deferpool[sc]) {
if len(pp.deferpool) == cap(pp.deferpool) {
// Transfer half of local cache to the central cache.
//
// Take this slow path on the system stack so
// we don't grow freedefer's stack.
systemstack(func() {
var first, last *_defer
for len(pp.deferpool[sc]) > cap(pp.deferpool[sc])/2 {
n := len(pp.deferpool[sc])
d := pp.deferpool[sc][n-1]
pp.deferpool[sc][n-1] = nil
pp.deferpool[sc] = pp.deferpool[sc][:n-1]
for len(pp.deferpool) > cap(pp.deferpool)/2 {
n := len(pp.deferpool)
d := pp.deferpool[n-1]
pp.deferpool[n-1] = nil
pp.deferpool = pp.deferpool[:n-1]
if first == nil {
first = d
} else {
@ -449,8 +376,8 @@ func freedefer(d *_defer) {
last = d
}
lock(&sched.deferlock)
last.link = sched.deferpool[sc]
sched.deferpool[sc] = first
last.link = sched.deferpool
sched.deferpool = first
unlock(&sched.deferlock)
})
}
@ -469,7 +396,7 @@ func freedefer(d *_defer) {
// both of which throw.
d.link = nil
pp.deferpool[sc] = append(pp.deferpool[sc], d)
pp.deferpool = append(pp.deferpool, d)
}
// Separate function so that it can split stack.
@ -720,7 +647,7 @@ func addOneOpenDeferFrame(gp *g, pc uintptr, sp unsafe.Pointer) {
throw("missing deferreturn")
}
d1 := newdefer(0)
d1 := newdefer()
d1.openDefer = true
d1._panic = nil
// These are the pc/sp to set after we've

12
src/runtime/proc.go
View File

@ -4784,9 +4784,7 @@ func (pp *p) init(id int32) {
pp.id = id
pp.status = _Pgcstop
pp.sudogcache = pp.sudogbuf[:0]
for i := range pp.deferpool {
pp.deferpool[i] = pp.deferpoolbuf[i][:0]
}
pp.deferpool = pp.deferpoolbuf[:0]
pp.wbBuf.reset()
if pp.mcache == nil {
if id == 0 {
@ -4864,12 +4862,10 @@ func (pp *p) destroy() {
pp.sudogbuf[i] = nil
}
pp.sudogcache = pp.sudogbuf[:0]
for i := range pp.deferpool {
for j := range pp.deferpoolbuf[i] {
pp.deferpoolbuf[i][j] = nil
}
pp.deferpool[i] = pp.deferpoolbuf[i][:0]
for j := range pp.deferpoolbuf {
pp.deferpoolbuf[j] = nil
}
pp.deferpool = pp.deferpoolbuf[:0]
systemstack(func() {
for i := 0; i < pp.mspancache.len; i++ {
// Safe to call since the world is stopped.

8
src/runtime/runtime2.go
View File

@ -613,8 +613,8 @@ type p struct {
pcache pageCache
raceprocctx uintptr
deferpool [5][]*_defer // pool of available defer structs of different sizes (see panic.go)
deferpoolbuf [5][32]*_defer
deferpool []*_defer // pool of available defer structs (see panic.go)
deferpoolbuf [32]*_defer
// Cache of goroutine ids, amortizes accesses to runtime·sched.goidgen.
goidcache uint64
@ -801,9 +801,9 @@ type schedt struct {
sudoglock mutex
sudogcache *sudog
// Central pool of available defer structs of different sizes.
// Central pool of available defer structs.
deferlock mutex
deferpool [5]*_defer
deferpool *_defer
// freem is the list of m's waiting to be freed when their
// m.exited is set. Linked through m.freelink.